1. Field of the Invention
The present invention relates to differential-pressure flowmeters and flow-rate controllers used in fluid transport pipes in various industrial fields, such as chemical factories, semiconductor manufacturing, food manufacturing, and biotechnology.
This application is based on Japanese Patent Application No. 2009-024714, the content of which is incorporated herein by reference.
2. Description of Related Art
Japanese Unexamined Patent Application, Publication No. 2009-2901 discloses a known example of a differential-pressure flowmeter and a flow-rate controller used in fluid transport pipes in various industrial fields, such as chemical factories, semiconductor manufacturing, food manufacturing, and biotechnology.
Two pressure sensors constituting the differential-pressure flowmeter and the flow-rate controller disclosed in Japanese Unexamined Patent Application, Publication No. 2009-2901 each have a characteristic such that an indication value changes as the ambient temperature (surrounding temperature) changes; that is, the indication value increases as the ambient temperature becomes higher.
Therefore, when a temperature difference occurs between the ambient temperature of one of the pressure sensors and the ambient temperature of the other pressure sensor as a result of a change in the ambient temperature of only the one pressure sensor, the pressure measurement by the pressure sensors becomes unstable, possibly causing a malfunction.